Few performance fixes

My apologies for all the performance issues with the last build. Here is a fixed version. I also fixed some of the other issues, such as problems with mirrors in some cars, cars with cosmic suspension failing to pass the ride height test, or some inconsistencies with rain physics.

Render stats app got some extra measurements related to frames pacing (which also led me to readjust some of the internal timing-related logic).

Oh, and also, the underlying physics library ODE (used for detecting collisions and solving joints) was updated a bit to improve collision quality and performance. There are a few related physics experiments as well. Nothing too important, but now, Assetto Corsa can handle quite a few collisions at once.

Thank you for all the reports, and all the support! Now, I’m going to collect reports for a bit longer, and, once everything seems stable, the public 0.3 will finally be ready. For now, here is a new build, and here is the full list of changes, please give it a test.